The present invention relates generally to etching semiconductor substrates, and more particularly, to systems and methods for dry etching semiconductor substrates and for cleaning the etch process chamber.
In general, the manufacturing of the integrated circuit devices (in the form of semiconductor substrates and wafers) includes the use of plasma etching chambers. The plasma etch chambers are capable of etching selected layers on the substrate as defined by a mask or pattern. The plasma etch chambers are configured to receive processing gases (i.e., etch chemistries) while a radio frequency (RF) power is applied to one or more electrodes of the plasma etch chamber. The pressure inside the plasma etch chamber is also controlled for the particular process. Upon applying the desired RF power to the electrode(s), the process gases in the chamber are activated such that a plasma is created. The plasma is thus configured to perform the desired etching of the selected layers of the semiconductor wafer.
Low volatility byproducts are produced in some prior art plasma etch processes. By way of example, in a copper etch process using chlorine containing gases (e.g., Cl2 and HCl), the byproduct is CuClx. CuClx is non-volatile at room temperature. The low-volatility byproducts typically condense on the chamber walls. During each plasma etch cycle, the byproducts build-up on the chamber walls. Eventually the byproducts build-up to a certain thickness. The byproduct build-up then begins to “flake” off of the chamber walls and is therefore becomes a significant particle source. The particles can contaminate the substrates being etched in the chamber.
The conductive byproduct deposits can also interfere with the operation of the plasma. By way of example the conductive deposits can short out and even extinguish the plasma. The conductive deposits can also change the plasma density that can significantly affect process in an inductively coupled plasma chamber. A non-conductive deposit can alter the electrode area conditions in a capacitively coupled plasma chamber. These and other effects can impact the efficacy of etching multilayered thin film stacks.
Recognizing that the internal surfaces of the plasma etch chamber are exposed to the plasma, the chambers are often designed to permit the use of simple lining parts, such as, disks, rings, and cylinders. Because these lining parts are configured to confine the plasma over the substrate being processed, these parts are continuously exposed and attacked by the processing plasma energies. Due to this exposure, these parts ultimately erode or accumulate byproduct buildup, requiring replacement or thorough cleaning. However, the cleaning and/or replacement costs of these lining parts can become very expensive both in actual cost and in lost production time required for the cleaning and replacement.
Additionally, the process chamber must also be cleaned frequently to reduce the particle contamination or variation in plasma conditions due to variable RF coupling across byproduct covered inner surfaces. The frequent cleaning requirement reduces the time the process chamber can available for etching processes and thereby reduces the substrate throughput of the process chamber.
In view of the foregoing, there is a need for a system and method for reducing the process chamber cleaning requirement and thereby increase the time the process chamber can available for etching processes.